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Ever really thought about this topic?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Dave_1, Aug 21, 2006.

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  1. Dave_1

    Dave_1 New Member

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    I need your input to confirm my suspicions. Here are the questions pertinent to this subject.

    Do most pellet heaters just burn compressed wood?

    Why is the flue size of most 50,000 b.t.u. pellet eaters only 3” while a Fisher Grandmother Bear, & other equivalent 50,000 b.t.u pre thru mid `1980 heaters, 8“ ?

    Why then are pellet eaters EPA approved even though such are not equipped with a catalytic (cat) converters while the pre thru mid `80‘s heaters are not?

    What is the known variable between the pellet eaters & the pre thru mid `80‘s heaters?

    Would such be the moisture content (mc) of the fuel (wood)?

    Is it not true that the 99.999% of pellet eaters never experience creosote?

    Is it not true that if the mc is 20% such wood is accepted as “seasoned” & therefore preferred fuel for any wood heater?

    Have you figured out the solution to making non approved EPA wood heaters EPA compliant? ;-)

    Dave

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  2. MountainStoveGuy

    MountainStoveGuy New Member

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    flue size has alot to do with btu loss, you comparing something that has no measurable efficiency with somthing that has upwards of 90% efficiency. Same principal that gas waterheaters these days have PVC for venting

    Pellets stoves burn clean because the fuel is injected by air and most everything is burned up

    True pellet heaters really only acumilate ash, the above statement is what makes this possible

    Unless you want to pay to have your stove tested by the epa there is no way to make it so.

    Hope that helps,
  3. begreen

    begreen Mooderator Staff Member

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    Do most pellet heaters just burn compressed wood? - no lots also burn corn

    Why is the flue size of most 50,000 b.t.u. pellet eaters only 3” while a Fisher Grandmother Bear, & other equivalent 50,000 b.t.u pre thru mid `1980 heaters, 8“ ?
    > As MSG says, efficiency and heat loss up the chimney. Pellet stoves have forced draft

    Why then are pellet eaters EPA approved even though such are not equipped with a catalytic (cat) converters while the pre thru mid `80‘s heaters are not?
    > Cause they burn so cleanly, like .9 gph or less.

    What is the known variable between the pellet eaters & the pre thru mid `80‘s heaters?
    > Lots, mostly efficiency, ease of use and major reduction in pollution

    Would such be the moisture content (mc) of the fuel (wood)?
    > Not really assuming the wood burned is very dry

    Is it not true that the 99.999% of pellet eaters never experience creosote?
    > Correct

    Is it not true that if the mc is 20% such wood is accepted as “seasoned” & therefore preferred fuel for any wood heater?
    > Ok

    Have you figured out the solution to making non approved EPA wood heaters EPA compliant? ;-)
    > Replacement works ;-)
  4. webbie

    webbie Seasoned Moderator Staff Member

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    USing forced draft, a Pellet Stove is able to force more air out the chimney.

    In other words, it is the same reason why a small fan on your desk can cool you, but you have to open a bunch of big windows to do it with natural draft.

    Woodstoves with flues larger than 6" are usually for reasons of large door opening size - so they don't smoke. A 6: flue can carry the actually smoke and heat output of most all wood stoves.
  5. Dave_1

    Dave_1 New Member

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    Msg,

    Thanks, but your statement that:
    is confusing.
    I was under the impression the pellets were dropped into a burn bowl while air was fan circulated thru the heater helping to burn such & expel the smoke.
    Is that right?

    Begreen,
    Points taken, but according to what I’ve read there was a 30% increase in efficiency in 1984, due to cat over non cat stoves, & again a 30% increase in the early `90’s due to pellet eater efficiency. Yes, the EPA also increased non-cat heaters but is vague on how they arrived at their efficiency #’s. Do you have a link that will help?

    I’ve also read that there are 7,500 - 8,000 b.t.u’s in a pound of wood, whether wood or pellet, depending on who one reads. Obviously the fire causes the release of that energy. Assuming that the wood in a heater is at the same mc as in the pellet eaters than the energy released is the same provided the heaters are operated at the same temp. Thus it appears to me that wood burned at 20% mc cannot have the same b.t.u. output as there is an additional 10% of water content that must be over come, which clearly subtracts from the b.t.u. output everything else being equal.

    Agreed?

    That being true the only difference I see is the fan being applied to the pellet eater in order to provide a complete & sustained burn. Sort of like sticking a cigarette out the window of a moving car (pellet eater) verses allowing it to burn naturally (wood heater) ?

    Right?

    So if the wood heater also had that fan blowing into the input air control, & the mc of the wood was that of pellets, then the heaters efficiencies should be close, if not the same.

    Agreed?

    Thus my question asked earlier & your answer:

    leaves me confused since you are in agreement with the rest of my points. Having established that the mc is the same in both operations please explain further "Not really assuming the wood burned is very dry"

    Thanks

    Craig, points taken

    Thanks

    Dave
  6. begreen

    begreen Mooderator Staff Member

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    Oy!, lots of points and questions. First, most pellets are at 8% or less mc I think. There is a lot more to the design of a pellet stove than the average pre-epa stove. The pellet stove is much more like a furnace than a woodstove. With forced draft, and very controlled combustion, it achieves a much more complete burn. This an acetylene torch before one adds the oxygen. Pure acetylene burns smoky and carbonous. Add O2 under pressure and one gets a fine hot flame. A good pellet stove also scavenges more heat from the combustion and thus the exhaust gases are much cooler. The evidence is in the ash. I could burn 500 lbs of pellets and have about 2 pounds of ash remaining. That's pretty complete combustion.

    I think the biggest advance that I've seen in EPA stoves has been greatly improved secondary and tertiary combustion. This means less unburned gases heading up the flue. That translates into more heat from the stove for the same amount of wood. They've also greatly improved keeping the front glass clean which is a nice benefit.

    Here's a link about early epa testing in our area. http://www.chimneysweeponline.com/library.htm Scroll down midway to the woodstove info section for lots of links and information. Also, here is a link that has info on combustion design, again about midway down the page. http://www.woodheat.org/technology/woodstoves.htm
    Hope that helps.
  7. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    The long and short of it is that pellets are more consistent, contain less moisture and burn more effiecinetly because they have air blowing right on them when they burn.

    Wood stoves have to depend on the dryness of the wood, the shape and size of the splits and how much air is drafting through the inlets based on the draw of the chimney.

    And if I could figure out how to make a non-epa performer compliant then I wouldn't be insert shopping. I don't care what my neighbor breathes. I just wanna keep the crap out of my chimney and get more mileage outta my wood.

    With apologies to BeGreen on that part. The jerk next door has a fleet of full sized pickups gas pickups.
  8. begreen

    begreen Mooderator Staff Member

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    A big difference with pellets is that one is only burning the fuel that is needed to sustain the tightly controlled flame. Stop feeding pellets and the stove goes out in short order. Stop feediing a big stove with a load of wood and several hours later it will still be burning. Wood stoves have to get the load of wood hot enough to burn, then char the wood and burn off the gases and charcoal. During that process, lots of unburnt gases go up the stack. That's inherently less efficient.
  9. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Rodger that.
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